Get 20M+ Full-Text Papers For Less Than $1.50/day. Subscribe now for You or Your Team.

Learn More →

Formation of 14C-Labeled Alanine from Pyruvate during Short Term Photosynthesis in a C4 Plant

Formation of 14C-Labeled Alanine from Pyruvate during Short Term Photosynthesis in a C4 Plant Abstract Large amounts of alanine are produced in the first few seconds of photosynthesis in Portulaca oleracea L. The normal precursor-product relationship (phosphoglyceric acid → pyruvate → alanine) does not appear to operate in this species since labeling in pyruvate precedes that in phosphoglyceric acid. Pulse-chase experiments show that the alanine is rapidly metabolized. After a 6-second pulse of 14CO2, the percentage of 11C in alanine drops more than 30% in the first 10 seconds of a 12CO2 chase period. The percentage of 14C in the other early-labeled photosynthetic products, aspartate and malate, also decreases during the 12CO2 chase. The decrease of label in these compounds is concomitant with an increase in the labeling of sucrose and alanine, which in this case is formed via phosphoglyceric acid. Randomization of label within alanine increases gradually throughout the 2-minute chase. Alpha-keto acids accounts for up to 20% of the total 14CO2 incorporated by young leaf tissue. Pyruvate alone accounts for at least 65% of the radioactivity in the keto acid fraction in both young and mature leaves. Other early-labeled keto acids are oxaloacetate and, in young tissue only, hydroxyphenylpyruvate. We propose that, in Portulaca, pyruvate is one of the earliest-labeled photosynthetic products and serves as the immediate precursor of alanine. 2 Present address: Department of Botany, University of Iowa, Iowa City, Iowa 52240. 1 This work was supported in part by National Science Foundation Grant GB-12964 and a Grant-in-Aid of Research from The Society of the Sigma Xi. This content is only available as a PDF. © 1974 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Physiology Oxford University Press

Formation of 14C-Labeled Alanine from Pyruvate during Short Term Photosynthesis in a C4 Plant

Plant Physiology , Volume 54 (4) – Oct 1, 1974

Loading next page...
 
/lp/oxford-university-press/formation-of-14c-labeled-alanine-from-pyruvate-during-short-term-QN8XeV9Hwa

References (11)

Publisher
Oxford University Press
Copyright
Copyright © 2021 American Society of Plant Biologists
ISSN
0032-0889
eISSN
1532-2548
DOI
10.1104/pp.54.4.608
Publisher site
See Article on Publisher Site

Abstract

Abstract Large amounts of alanine are produced in the first few seconds of photosynthesis in Portulaca oleracea L. The normal precursor-product relationship (phosphoglyceric acid → pyruvate → alanine) does not appear to operate in this species since labeling in pyruvate precedes that in phosphoglyceric acid. Pulse-chase experiments show that the alanine is rapidly metabolized. After a 6-second pulse of 14CO2, the percentage of 11C in alanine drops more than 30% in the first 10 seconds of a 12CO2 chase period. The percentage of 14C in the other early-labeled photosynthetic products, aspartate and malate, also decreases during the 12CO2 chase. The decrease of label in these compounds is concomitant with an increase in the labeling of sucrose and alanine, which in this case is formed via phosphoglyceric acid. Randomization of label within alanine increases gradually throughout the 2-minute chase. Alpha-keto acids accounts for up to 20% of the total 14CO2 incorporated by young leaf tissue. Pyruvate alone accounts for at least 65% of the radioactivity in the keto acid fraction in both young and mature leaves. Other early-labeled keto acids are oxaloacetate and, in young tissue only, hydroxyphenylpyruvate. We propose that, in Portulaca, pyruvate is one of the earliest-labeled photosynthetic products and serves as the immediate precursor of alanine. 2 Present address: Department of Botany, University of Iowa, Iowa City, Iowa 52240. 1 This work was supported in part by National Science Foundation Grant GB-12964 and a Grant-in-Aid of Research from The Society of the Sigma Xi. This content is only available as a PDF. © 1974 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Journal

Plant PhysiologyOxford University Press

Published: Oct 1, 1974

There are no references for this article.